Brave Helios wake up your steeds, Bring the warmth the countryside needs. The Moody Blues, Days of Future Passed

Assignment: Study for your final exam on Tuesday, 13 December at 8:00 am in the Theatre in Coleman Hall. Review Session on Sunday, 13 December, at 11:30 in Carnegie 208.

In Class: Question to Ponder Currently, what is our best evidence indicating that life exists or existed on Mars? a) Satellite photos of friendly martians waving at us. b) Soil samples from the Viking mission in the 1970's. c) The structure and chemistry within a meteorite believed to be from Mars. d) Fossils found by the NASA rovers currently on the martian surface. The Sun is BIG far and away the biggest object in the SS even Jupiter has a diameter 11 times smaller it would take 110 Earths to stretch across the Sun's belly Size is what makes the Sun different Producing Sunlight enormous mass creates enormous pressure and heat in center of the Sun temperature in the very center of the Sun is 14-20 MK at these temps, hydrogen can fuse into helium nuclear power --> generates enormous energies this heat works its way to the photosphere The Photosphere sort of the surface, but since it's a big gas ball it's tough to talk about a "surface" kind of like the edge of a fogbank this stuff is heated to about 6000 K and glows no "burning"; we just see really hot glowing gas Sunspots Regions of concentrated magnetic field. insulated from surroundings, these regions cool appear darker Sun goes through 11-year sunspot cycle, from active Sun (e.g., lots of spots) to quiet Sun (not so many)